A 40 mm round is needed that would release sub-projectiles from its payload in a manner which controls the spread of the sub-projectiles for a desired range. Early design attempts to meet the needs previously discussed generated concepts similar to a traditional shotgun wad which rapidly releases its payload as it exits the muzzle of the weapon. Currently the only 40 mm solution to this need might seem to be an M576 round. The M576 was first developed as a close quarter solution for grenadiers in the Vietnam War. The cartridge was intended to disperse a payload of buckshot similar to a shotgun shell for use in close quarters and in environments where traditional 40 mm grenades would be ineffective such as shooting through brush. A problem with this cartridge is that the shot cup is designed to tumble in order to disperse the payload, causing a large spread of pellets at the target. Due to the need for an extended range solution this concept is seen as not feasible since the shot spreads too rapidly to be effective on a target. Even in a smooth bore shotgun barrel firing a shell with a traditional shotgun wad results in too great of a spread to be effective for the given ranges needed. The problem of spread also is exacerbated in weapons which have rifling, and shortness of barrels (such as the M203 and M320 barrels).